1. Field of the Invention
The present invention relates to a filter made of a resin which is suitable for use in an ink jet apparatus of printing image information on a recording medium by flying ink droplets to said recording medium and to a process for the production of said filter.
2. Related Background Art
The ink jet printing system is to discharge ink through a minute nozzle whereby printing a character or image on a printing medium such as paper, cloth, plastic sheet, or the like. There have been proposed various ink jet apparatus having an ink jet head of such ink jet printing system. These ink jet apparatus have been often used as printers serving as power outputting terminals in copying machines, facsimile machines, word processors, or work stations, or as printers of the handy type or potable type installed in information processing systems such as personal computers, host computers, optical disk apparatus, and video apparatus.
Now, the ink jet head employed in the ink jet printing system generally comprises a discharging outlet for discharging ink, a liquid chamber for storing ink to be supplied to the discharging outlet, an ink pathway of communicating the discharging outlet with the liquid chamber, an energy generating element which is disposed in a given portion of the ink pathway and which serves to generate an energy for discharging ink through the discharging outlet, and an ink supply port for supplying ink into the liquid chamber from the outside of the ink jet head. The ink to be supplied to the ink jet head is supplied from an ink container through an ink supplying means. A filter for ink is usually disposed between the ink supplying means and the ink supply port or between the ink supplying means and the ink container. The ink to be supplied to the ink jet head through the ink container is flown into the discharging nozzle through the filter.
The filter used herein is required to achieve the following roles: (1) to prevent the nozzle from being clogged with contaminants such as dusts, small ink masses, or the like contained in the ink whereby preventing occurrence of non-discharging or a variation in the ink discharging direction, and (2) to prevent air from entering into the liquid chamber whereby preventing occurrence of instable ink discharging due to a decrease in the discharging energy.
As for the position for the filter to be disposed in an ink jet head, it is desired to be as close as possible to the nozzle (the discharging outlet). The reason for this is that in the case where the filter is disposed in an upstream portion of the ink supply system, although ink in the ink container can be filtrated, there is a fear for the ink to be contaminated with air during its movement until the nozzle (the discharging outlet).
As for the filter itself, it is desired to be as smaller as possible in terms of fluid resistance for the reason that especially in the case of driving an ink jet head a high speed, the ink refilling rate is decreased as the fluid resistance increases, resulting in imparting a negative influence to the high speed driving.
The filter in the conventional ink jet apparatus is constituted by ceramic, capillaries, fiber, plastic, or sintered body. In the prior art, as for the filter constituted by any of said materials, as it is difficult to be disposed at a complicated portion in the inside of the ink jet head, it is usually disposed at a given installation portion which has been intentionally established therefor. Such installation portion is established typically at a contact portion between the top plate and the ink supply pipe or a tip portion of the ink supply pipe, respectively of the ink jet head. However, in any case, as for the area of the installation portion for the filter, it is unavoidably governed by the size of the ink supply port in the ink jet head. Accordingly, there is a limit for the area of the installation portion for the filter. In this respect, the filter is necessary to be designed such that it achieve the above described roles within a limited, narrow area.
Further, in the case of fixing the filter to any of the foregoing filter installation portions, there is usually employed a manner in which the fixing is conducted with the use of an adhesive or another manner in which the fixing is conducted by way of welding by means of ultrasonic vibration or heat. However, any of these manner is problematic. That is, as the fixing manner with the use of an adhesive, there are disadvantages in that there is a fear for the filter to be clogged when the amount of the adhesive used is excessivel great, and there is another fear for the filter to be insufficient in terms of the adhesion when the amount of the adhesive used is excessively small. As for the fixing manner by way of welding, there is an requirement that the installation portion for the filter be designed to be in a desired form so that the welding can be readily conducted, and in addition to this, there is a restriction for the kind of a material as the installation portion at which the filter is to be installed.
As above described, it is generally known to use a filter constituted by a sintered body. In this case, although the situation is free of the above described problems, there is a problem in that the fluid resistance thereof is difficult to be estimated, and in addition to this, there is another problem in that it is necessary to expose the ink jet head to high temperature upon conducting the sintering, wherein an negative influence will be imparted to the ink pathway.
Thus, as for the conventional filter for an ink jet head, it is understood that there are such problems as above described because the filter is produced separately from the ink jet head and thereafter, and the filter obtained is then fixed to the ink jet head. In addition, there is a further problem in that in order to precisely dispose the filter at a limited, small portion in the vicinity of the discharging outlets of the ink jet head, a well trained skill is required.